SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '56d7c56d97baee211268c2249e45c366c6840a80b44ee3df234a298f1a894790' 
  AND token = 'CAVDq23pXuu/LyZJhoH3wmCxFbvE7lYymwAUhT0vGx4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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