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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '878b910e3e3775d6f05bcd18b9a0d5889ad83a21e16ab3dd3fbb3c418bdd76c8' 
  AND token = 'Yep9xrTiGjUg7RTB8+1FCEeth4z/J9ekjDlKae0OLs8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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