SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76a6d5323e925c0937a522f16c1366507e2a30dc9f273df75e7f0b84605d84a4' 
  AND token = 'vltT0G/5sXKxGYCfAXMsnyIB+/q9xUoB6lAFmFa8ajw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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