SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b775874b463f4faf983226859a8f55a7371ab332df34dacbaff96d5cf0457897' 
  AND token = 'R5QLW5vja0zgy8v4zcyDPbwLXRRoXD31oEfsc/M+A10=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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