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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '151e3c82add30a88a6033d474a6b659a7480210876715290e6dd04ab53f42a54' 
  AND token = 'PROtXn6KIVKH4ySXLUdulAIL287r5kp3SYfs/2CdFb8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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