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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83f712dce762dd91a6a81b153b434c25d10a04f78335d8dfd1329ff9fc9ba3e9' 
  AND token = '1dVFaNMiO7KIEtUDcq/PFmNHFy+6g3WwLrFT53WZkgY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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