SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8a51f0bc08753d42fba9484c8445d45691ae296b19b633477cb8590abbea3313' 
  AND token = 'f2OzPlvqe4lSpa8JTHN+1WKRnAnm+WZ+3lKUtfpokPA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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