SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '793708acfee3d9b1fe133963c0fef43b137ebdb058ae43b615aa85ca4ea01673' 
  AND token = 'AfAjweEk73hKirGMrhB9++Synwf4uGhP/fR7jdtMmLU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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