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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c3c4d6a07b38557c4fa2fea79a74786b85e1b49e865ed70a7418263c7f9080' 
  AND token = 'Tr/SvZa84i488Tb5eYYLVSTXnjHDDR7T5t+wmA0EWWM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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