SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8199121688dab4f9203e60b14cdff2a515fb4d33c79f08c936991ab1a701a1e' 
  AND token = 'ChJFq48M9RMjxswHhIwjvLPI+ZxBdeqh3YhAKNl2AFM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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