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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd55b34b4a4faf28fc4dd89ff76de256c4d8ffcf8b4dd411838c2458cd8c9fd68' 
  AND token = 'nBFiISA3K/dHKbNQetW4qXrE/Ocp+mfd7anTa5nsCWY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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