SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b3c6693021dc94581769c3a4669c750589565d50803dcf6b4412751c94c4b22' 
  AND token = 'rD76ylOSDl20pHkUS2Eeu1n1sjr46pv8nXSPmXa7DI8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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