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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e4e6802e1dfed551923db685bed3950490a6c1a63189e4d0d8befc8dbe92a2f' 
  AND token = 'P0BFD/aqSnYKiqy2pqW/j0oVPQ7Qgfpt8cQ9SGG5R1s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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