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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c7db8b6d4cbb8ad8324a2f00bf93a3bbb5b1013edce4abf442bcece82bd0df79' 
  AND token = 'zDsCV52sbwxClj8ywtIGMjPcBTmtBlLJsfi+CnsVQaY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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