SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '21f4b2f407de10497a693a31e6588156d2bc6ce348a0cdce97521ec06850fd39' 
  AND token = '8TTCmiZaM4GTlAACCENIRH61VS06GedB/dMU81Pb2s4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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