SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '21c602c9558de997dc6eff17d79a67899f6af7a4da4a85d875bf6645a666c836' 
  AND token = '12zyB+rf5r44fEnMxOA5KpRY7hhHWFrMfga7+dB8RIM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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