SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '876922e1b51df8cc3013339a873ceca578496ce6d542984f6d4910e90e754090' 
  AND token = 'RGqQf5PczWF9OoNqggW42w+DKNan1s87uFG0j6LElRA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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