SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76ef0008ea1ca3025a118f70cb53be3a51a818f766c47068f8a7ca2cc7fa4e54' 
  AND token = '2uRwnmGNFIhLfOUuQ3qnSvCqLHlB4XJZiL21vqzHYRg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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