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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '869a21830bf9d047a0b13bb126099583eff2ed99769673e3de5fafa43924d81d' 
  AND token = '8j0U7tfUiD/KAO0blKa5lJhYBDRc6adgLzOJ/F9t9g0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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