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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75ccd9d0721d8c8e2e0da94a47070f643713e317bdd0aa9023ba37311b7c78dd' 
  AND token = '3nQjOlFS0vQw3ZZ8JEqnIf0iqVP3tw37UcSqCZSwLJE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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