SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '49fffc906a415353fc924d3488b858836d02270f96600bec94e5e23a94df3287' 
  AND token = '9vSl7VmSBjFVkFSqsgaHxQzUO7zfXazMJiizsRC/wLg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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