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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6f662ff40fd0019b29ade9ac7dbb5444dffb30b09fc5b0c7007c00027ee2f57' 
  AND token = 'vIZ4jrBayRGvMe/TR/BH8yG/9LrP2GOdCMIQJjW4vE8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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