SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3d5777502f971ba82d0a96928465fc1b506677712af298ee01f56e9cbebe051' 
  AND token = '20+uX9Izd0YI4lVUpncB+2UVPldbT15kyp3KWZvfgwc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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