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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1b6c6255d01c7cc7e9b6acac2a4de712d4762fd2b7314467fb047d5459d491e9' 
  AND token = 'Hi8QnXvxkUx9AbEiQQGT+8uxwNZNOXG1bvzubxOtuIo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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