SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a4b638f4581199794df50b209589d16794708875262c6ce06c10bfad8ac5d07' 
  AND token = '8k4xKEwBIA+RNUNYY2ECXg+2Phlv135qir9Nx2ryrdo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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