SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b7beaed3e9b044b85ab0f87509c6da85c95c1180bc6a832c5dbb279a18094d' 
  AND token = 'WN+XCMd3Ek4/QsuiUzZDqRZZ0oyMCDoMuWekTnJly1o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00013

JSON explain

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