SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9e21df4ea349c3bc8a517264de0e356443787e0fa9b4bb37b12add8a48435440' 
  AND token = 'P0o2A40jVOwf8r0AyYBFY+0py0IIZowsD0sKo8jr1zg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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