SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a2537598af95d43d745b29024995099df7d780e66c317cd2b5ba224b5ef5fee8' 
  AND token = 'KMy7sCyyt5I9Lb/C+GE5YsczUK34jnaxU0Ibv93Ejxw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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