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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '70ed83abaaedbbdaf2f0a2a096cb9b4331f934862d6e3beb1d83484a1ecfb7c5' 
  AND token = 'xKLibFJPZ0tAOxiAmvcVqH1afKcUnPuIAr+pywWORBo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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