SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '20e60dec386b5ae0575bb770a9f235eabb31d26350399f2d2aee26a358aab242' 
  AND token = '9Q609R/5iTIy2uRdcdNIIybx95NwacSK4obmoVtJlm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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