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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b21a25d6d578ab2520db731eabfa6d9e8d459862f81c2a9b0ad8a9d766940bda' 
  AND token = 'zR/cfeKV8VwCO2wTaRYhB2rLR0nqTQIKC1o9wZ2Cyd0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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