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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '875a9d21b7f360fcd4ce5d6e1c260d4ef106b4fea14dbe1a57ea51b9d7376349' 
  AND token = '8U3CgNHCs+h/HHzXXNT8KpiSV1P9YLHklpxyfotoN88=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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