SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15b76987931adaf4a7b6454ece25d09ef38523ef2447c251602f12d7fdeb8dd1' 
  AND token = 'osZqrQ96k0UjDFVLev1+gjabTKogcrL2766CRhmoKl0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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