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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51204082d1b3ff912051bcc349a9594a71b69f52a477ccce3d1fc547d254fa9e' 
  AND token = 'RKaXbm6eXL3ZNaqDgyCC4Eh87oECEhJxh27tb+2EspQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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