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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '340e7904a6b08d4163a5795c43557e8876c979f491b7246d931fe0305ff3ed4c' 
  AND token = '5PfFlTNV+VujGSIJ8SsuOCYtc2fFL0LHdVPW5jJGGXM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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