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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fc3700eb67d2c7404a7143913de1f20c54962ce85ee944fb20695ce40a875f51' 
  AND token = '68G9MvEZLMmobU6yEWiSfSQRo7bUBhMM/VssOz01mcI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}