SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4f3b97d4cb5fdc2631aa0e8e88147b9a6926602451acbde9f2074ba3cc36b968' 
  AND token = 'x0UND6Jyvnt81pb4+Bv7GGZqEbPf+ag3sQOeXQ9enDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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