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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a77621546a8a554f9d7eeba9066614b71de507b09023ee17673b7209d1dbac25' 
  AND token = 'u/x49u2rdVgtL6q4Re+sdcErBEPk8881kxwFuGOJglQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}