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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6d7c51fdb1a3dd6bf3e24b10cf5084b045e56e2a7f9c8b8fdaf252042a49642' 
  AND token = 'YpIMNy88rMZ6PxCmJthBcZeEJduCheBKB1FeFQ1GIvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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