SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b98cc4212224174fa9029e01fefacfbb8940012100f91329b9d21ca959bf6bf2' 
  AND token = 'r8mOiPTJTofrV5B+5xzPUNhpT2m56sUVtblS35DQcV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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