SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '568651ea583f088cbacda421773c0b7a738f552c851807bcdaba889008aba753' 
  AND token = 'TIRPCuCShXsxcKt/f692jPbC4BZCAls44C5MtUtuDJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00055

JSON explain

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