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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '390ee8d0e1e6ab56fa66306df9bc6c4a9f08341c9deb8a4eb70d18d52460c8f3' 
  AND token = '6+lgO6sY7fwtVVMaXH5Z3vnKxFFPYa+Mgc95FMdNsec=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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