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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'be374338a1678daee8f365349ce809cead993f3801db512946a415399ef66937' 
  AND token = '/hX1Ke3TfisPZ0SGW5Vv+nOxFLBKacobF7x67j0hgko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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