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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8447a0d83a2b32034559effa976d59d41bb15fbe4078c68ad05a9d87b96e5cdf' 
  AND token = 'WsSOfieJKt2dAqTtHUVOmXmxs2ZCdwpt8FOd5Qqc/dg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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