SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5cf7fa0de30c0d2d29aa210bf89928dd3a2ca7eb81101127d5683aa06d9bd822' 
  AND token = '2jyyMRsZnpiupDe95tszPd+eKEEq1Gm/rQG8eIlLtK4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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