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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '811951a08a2034b8995d1eb6e9fa1451c494f566f821c970be6e7dbb5c164a4c' 
  AND token = '6/FSAFARqZtw3uwsPydx25sacYpBCl8RM04g8vin0fY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

JSON explain

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