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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ef03b3e2d8dd48ca7fdcb0bf9e9042cb956906dd2dde0f2439c46912a744a6da' 
  AND token = 'OF+1P3WjZYHvPD7Ju/+W+OAr24wiH9Uj++zciUMJdDA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}