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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b6889d7ca9a4012b4e08acf0f92da0fcfed845a7ee6f7bd52c92fcfe8e57b6' 
  AND token = 'DcMJsPONG7xMjonKL9MAKbsDvr+RMnDGfO4hNnsJ0mU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00045

JSON explain

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