SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6875875aeb906a08a422037821ed7858d2e5e47f5261a30535feaa0e89088749' 
  AND token = 'f0guzv3kX8R/QFYELvMcFCsgkZ8iVWKaxfFfxfPCWVI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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