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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4d57c1d6ffd94adfdb674a4fd3d37d620d80cf0a70c1453e7fed9aa256543f8' 
  AND token = 'QGT3z5IUiHnOR7czzW7S8RhDDwMz3IgqfaMGiOWc5Vk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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