SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a8ecc34dab447894f4d8fce255075d2c65310198f6e752f16da8cc9ccf7aa8' 
  AND token = '+27DBTqKTFhOOINGhdsQHGudXswDu8LJOjDA6fD/BUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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