SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e0eeb476c1df800d95530cd685d9ebfbb339edd6a80916df7643962e5a7bdd38' 
  AND token = 'KLbncfaTtP2mSEXqJLmR9aSoxgAz5lQIVU8telnPRak=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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