SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef40832aa0a798b40939226f2961106fa669649cc92e850bfda090a65c00f0fa' 
  AND token = 'tj2RSWQ3V+/7S6XP8o9wlc58//CkH0smq1FEluWvyE8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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