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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '686a7ba88c6049d4376e6d97ace40b581c76b0d3aea25cd2aa692896da46e2e8' 
  AND token = 'vDnAoIoHzfDFxNRLdZLAXpc6En+fzpBbpBBqpmPllhg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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