SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a604d69351091f252a17567f511596e5d6ad2280443267d91d0424181e07c8af' 
  AND token = 'h0yIr9KIK+FGGuOmNYmERqtWD+zeprBYgV9EMRVw5hI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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