SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c4140afb97ac5203faf32594776a142859aa0f9839cc00c213a6d28782076a54' 
  AND token = 'rMMFqRIDTGiKx0Nuhfs6ZTq5BjUvByt+cURoPpJvPhE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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