SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'b877f2efabf17992ccf70a4db46e4895f234b0837f138a977f33fa1f6450d16a' 
  AND token = 'mjmxXLtbVCZJMwzIIzTo3S6cE+4bfCzIWbIgzC7Fhu8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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