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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4750f9c1485dfdec91cb7f85c5b5e4fee9b9e895f3a55bfc6dfa403d104f80d' 
  AND token = 'N51jfg9nnRBgb3LatfrvZd1q2ckNi2MsavHq/8mWTA0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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