SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '53d2a4d51814100276e56df9533c0192bccea5c6321d4b37c56735a130a76b84' 
  AND token = 'gA/fkmtz3jMBgQKudqrgVf5T6xCRva/w8wfzxNMLF/c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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