SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '108620545b161e432a3ed939154cb6024ebd0a66fdab4597581de6fb8b42a52e' 
  AND token = 'h5r+JnySQzrHmDhPJQwvPLeGyYyP4XOz7AAShPXAeSg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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