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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b571c81a2cab693c6e7397e2ab1f0dbca4ed4366c1122bbc8562a276cf027ca3' 
  AND token = 'Mk6IGrRhAjE1w7bZtBBIn7T+B1y1aVVD7k/4QhA0yy0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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