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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c6ad7a04ee8780b2538a1d0b0c02bf2ec483e12208d15568646eab24aaab40f' 
  AND token = 'RexBhy8qVFwwo2wGcnau42scOgIHFEpkLeE88KfQY4M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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