SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '66f4e1664d4023ffc3daa78585188e499d12231b2bc9aacddeec5a494e04b5bc' 
  AND token = 'ELQMIA8YrSuhGUOK2ejJQGtJzzsQkVGGPmW/ApGynRs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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