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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a690adf6a40f7a61930441a63651d266ffaa461f22b995498da38b85d68fd38' 
  AND token = 'cXj6nCoykbmZUFAFZ+nZEZb9eUK4wh1OCeCasrxFY20=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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