SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '31fdc0d279ac32525279b73a40337af48c0094b71669b01b403c989b0a3240f6' 
  AND token = 'ClIydbtXVVzeh418UnrN3mV8iggd18zWgXXslyHW3eI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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