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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b53a5f62e3c1f6d7eb4be7d0243affc545dc129e61dc8c1229eea8a5332a402d' 
  AND token = 'DqZp+TV5Eor7ItEykBZDK3LpE8a3LL19IQEbiVxYNMo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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