SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b55c374095fdce065d443929735226ffbc2ac2c9fc99439ecf730c5b36249274' 
  AND token = '+BwcqYF4IzH9nu+gljwsi0J5Oy+yXZGMzxFJUENQCDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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