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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51319e5bc42dd7b6b618a19a119f9e9318cf88fe0aaef898212b9bd8f7aebb8d' 
  AND token = '+DgHv0CN8Mpph/InifGCBFPQ4Jv8ceRa6Kz3gQTnU0E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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