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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f18d2bf8bd2471f6e9823afb18552d34b9c178d3cf12e7d1ee05fe9f91f54e63' 
  AND token = 'bJ+Avm4PHU08c/omKJtp62ThiM8dLZG6GIinyx+vMhQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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