SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f6e4cce0fccfdfe6021afb817cf4e33237d09adb32c9b4a944ee8e42d216a023' 
  AND token = 'X8zmKpRRI6dVKdB0S2+iHaXZvVEiHf+mfCtbMlBjYO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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