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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a7d1377306f6ca2da5a28119b4700decf55df49be4e55907429acdcc2a493468' 
  AND token = 'q1Hc2vzEQzSrxKh2kirP45RF+TifXQF60kRY949OTmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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