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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c708d861dedd946ff72abb6818b3740d1f1171af3e24e17860ef5fcedb5cddd5' 
  AND token = 'xTpPOI+wTqxLTymI3EDepeQv79lUU2Dr9rqtZysS8SE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}