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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2831935bbd36e3003873536820f90efe004cd9d95401c644e8fae57e4ea4bd1f' 
  AND token = 'Dhp3oxAfRBr6UrpDwxLE2ElN7LEzr2F5nT2kvvD4Tmg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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