SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f9ca8dc140a1aeef553a234f53e83c8095e34c27f9486eb2f07f9fb3f8d8d01d' 
  AND token = 'QtcJiw6o1DDsvVGqQPXFWUF8LyS/0CeqSgwhjDglSzI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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