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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'df13dd929cd1243aca1edf5fb946d48768d8f790211ec35cdb8aac49c7bc0103' 
  AND token = 'WTjKUi89Fw5TU1ZaaSfaOGgj+w667AWfOoj5xCuCJJU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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